The present invention relates to vision-guided robots and, more particularly, to methods and apparatus for calibrating a vision-guided robot.
Manufacturing operations have now become automated to the point where robotic devices, without human supervision, perform many assembly functions which formerly were performed manually, or manually with a power tool. This evolution is evident in the assembly of automobiles, where, for example, robot devices perform welding operations and apply gasketing material to windshields. In applications where the workpiece may vary somewhat from a precise, predetermined location, it is necessary that the robot have the capability of detecting, with precision, the location where it is to perform an assembly operation.
To accomplish this, some robots are fitted with a camera and slit light projector, the latter component producing a target image on the workpiece which is perceived by the camera. A computer control compares the target image received by the camera with a stored target image and directs the tool carried by the robot to a precise location relative to the target image to perform an assembly operation.
With some designs, the tool is mounted at the end of an articulated robot arm, and this arm also carries the camera and slit light projector. In order for the assembly operation to be performed accurately, the spatial relationship between the camera, tool and slit light projector must be set and maintained.
Currently, such calibration requires the camera and slit light projector to be adjusted manually in spatial orientation relative to the tool. Such manual adjustment requires the positioning of the camera and slit light projector on the end of the robot arm to a precise, predetermined orientation.
Manual calibration is often accomplished by iterative trial and error techniques. Accordingly, there is a need for a method and apparatus for calibrating a vision-guided robot which eliminates the manual repositioning of the light and camera components.